Electrocatalysis: Development of electrocatalysts for
solar fuels
Applications of interest
1. Fuel cells
2. Electro organic synthesis
3. Other industrial electrochemical application
4. CO2 Valorization
5. Green H2 production
Interesting reactions
Reaction Yield Reaction conditionsTR
LApplication
HMF + 2H2O → FDCA + 3H2 90% Ni20 - 30 0C, atm, water
pH 12-135 Plastics
PDO + H2O → Lactic acid + 2H2 80% C30 - 40 0C, atm, water
pH 9-103
Plastics, food,
pharma
Furfural + 4H2O → Maleic acid +
CO2 + 4H2
80%Pb
(V2O5)
20 - 35 0C, atm, water
pH 03
Plastics,
building block
Levunilic acid + H2O → Valeric
acid + O2
>95% Pb20 - 50 0C, atm, water
pH 03
Biofuel,
cosmetics
Levunilic acid + H2O → γ-Valerolactone
+ O2
>90% Pb20 - 50 0C, atm, water
pH 7-82 Green solvent
Pyruvic acid + H2O → DMTA + O2 60% Pb RT, atm, water pH 0 2 NA
CO2 + H2O → FA or CO + O2 >80% Sn/AuRT, 0 – 80 bar, water,
pH 6-92
Building
block/fuel
2H2O → 2H2+ O2 >90% Pt TiO2
RT, 0 – 80 bar, water,
pH 6-92 Fuel
CO
H2
Renewable energy production in The Netherlands
05/05/2016
Data source: https://transparency.entsoe.eu.
Own graphic
28/11/2016
00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 24:00
0
200
400
600
800
1000
1200
1400
1600
1800
Re
new
ab
le e
ne
rgy p
rod
uctio
n /
MW
28/11/2016
Solar
Wind Onshore
Wind Offshore
Other
10000
12000
14000
16000
18000
20000
To
tal e
nerg
y d
em
an
d /
MW
00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 24:00
0
200
400
600
800
1000
1200
1400
1600
1800
Re
new
ab
le e
ne
rgy p
rod
uctio
n /
MW
05/05/2016
Solar
Wind Onshore
Wind Offshore
Other RE
8000
10000
12000
14000
To
tal e
nerg
y d
em
an
d /
MW
Energy storage technologies
Source. Specht et al., 2010
https://www.energysage.com/
Solar fuels. The idea
CO2
capture
Valued added
chemicals and
fuels
Direct light activation
Energy
World Meteorological Organization, WMO Bulletin, Tech. Rep. 12 (2016).
Close the carbon loop
Electrocatalysis Photocatalysis
Step 1
Renewable
Electricity
Solar fuels
2 steps process 1 step process Direct solar
light capture
Step 2 Electricity to
chemical bonds
H2
Modified
Fischer-Tropsch
CO2
RW
GS
Methane
CO + H2
Methanol
Formic acid
Water splitting
- H2O
- H2O
Raw materials for chemistry
Routes CO2 into fuels. Electrocatalysis
Fuels
Fischer-Tropsch
Nanopaticles
5 nm 15 nm 50 nm100 nm
Spheres Rods
1000 nm
Control size & shape
500 nm
Synthesis scale-up
13 December 2018
Synthesis scale-up from 1 ml to 10 L
10L2L0.001 L
Electrodes preparation
13 December 2018
Ultrasonic spray Coating
Photocatalysis- Plasmon activated
13 December 2018
Why hydrogen?
13 December 201813 | Photo Water Splitting (PWS)
Key role for sustainable future
Energy carrier
Electricity
Mobility
Heating
Chemical reactant
Fertilizer production
Oil refining
Solar fuel:
harvesting the sun
(e.g. 𝐻2 + 𝐶𝑂2 → 𝐶𝐻4 +𝐻2𝑂)
Why water splitting?
‘Grey’ versus ‘Green’ Hydrogen
Steam reforming
Fossil fuel based
Additional heat required
Very low price (1$·kg-1)
Water splitting
Possibly based on renewable energy sources
Electricity required
Expensive (6 $·kg-1)
13 December 2018
H2O
O2
H2
H HH H
H H
Steam reforming
Water splitting
14 | Photo Water Splitting (PWS)
Why photo-water splitting?
Two different ways of
producing green H2
‘Direct’ is the integrated
approach with highest
efficiency, and benefits
from heat
‘Indirect’ depends on
electricity price, suffers
from large current, but is
more mature
13 December 2018
H H
HH
H H
H H
PV-electrolysis
(indirect)
H HH
H
H HH H
Photo-electrolysis
(direct)
Current ≈ 1 A·cm-2
Suffers from heatCurrent ≈ 0.01 A·cm-2
Benefits from heatHigher
efficiency
Lower
efficiency
15 | Photo Water Splitting (PWS)
How do we split water directly?
Different approaches
Photo-chemical Photo-electro-chemical
13 December 201816 | Photo Water Splitting (PWS)
How do we split water directly?
Photo-chemical water splitting: oppertinities
Particle based system (slurries)
Low efficiency system
(very) Low cost
Safety to be addressed by processing
13 December 2018
Low cost of green hydrogen
17 | Photo Water Splitting (PWS) Maeda et al., J. Photochemistry and Photobiology C: Photochemistry Reviews 12 (2011) 237– 268
How do we split water directly?
Photo-chemical: development
Typical materials: TiO2 combined with co-catalyst (e.g. Pt)
Tuning light harvesting, suitable bandgap and (photo)corrosion
Research on commercial and non-commercial catalysts
Durable catalysts
Aiming at cost efficient water splitting
13 December 201818 | Photo Water Splitting (PWS)
How do we split water directly?
Photo-electro-chemical: opportunities
Device based – resembles a PV panel
High cost
Potentially very high efficiency
No safety issues
Yielding pressurized hydrogen
13 December 201819 | Photo Water Splitting (PWS)
Low cost of
green hydrogen
0 30 60 90 120
0,00
0,05
0,10
0,15
0,20
0,25
0,30
0,35
0,40
Curr
en
t d
en
sity (
mAc
m-2)
Time (min)
Dark
Light
1,23 V
0,0
0,5
1,0
1,5
2,0
Pote
ntial ap
plie
d (
V v
s. R
HE
)
How do we split water directly?
Photo-electro-chemical: material development
Typical materials: CIGS with Si-solar cell
Tuning suitable bandgap, required voltage bias and
(photo)corrosion
Scale up of photoelectrode manufacturing by ultrasonic
spray deposition
13 December 201820 | Photo Water Splitting (PWS) Van de Krol et al., in Photoelectrochemical Hydrogen Production (2012) 14-69
When is al this realized?
13 December 201821 | Photo Water Splitting (PWS)
Price vs. Performance: difficult to beat ‘grey hydrogen’
Photo-chemical Photo-electro-chemical
When is al this realized?
13 December 201822 | Phot Water Splitting (PWS)
Price vs. Performance: development
Focus on stability of materials, rather than high efficiency
Tailoring specific chemistry for large centralized vs. local
decentralized operation
Producing H2 with purity and pressure for industrial scale
directly
Device integration for local energy harvesting
Electrocatalysis vs. Photocatalysis ?
Location.
24/7 vs. day time.
Centralized vs. decentralized.
Return on investment.
13 December 2018
Carbon capture storage and/or utilization ?
CO2 concentration.
Location.
CO2 taxes.
13 December 2018
Green Hydrogen
Subsidies and/or CO2 taxes.
Centralized vs. decentralized
(Photo)catalyst durability.
13 December 2018